First make equations for both.
PLAN A
y = 0.08x + 430
PLAN B
y = 0.05x + 607
We need to solve for x to see at which point both plans are the same. We know that when x = 0, that Plan B is better. This means from 0 to x, plan B is better.
0.05x + 607 = 0.08x + 403
0.03x = 204
x = 6800
So this means that when the pay is more than $6800 then Plan A is better